PROJECT ABSTRACT Programs that improve housing quality, stability, and affordability present an important opportunity to intervene on a social determinant of child health and wellbeing, and child health is known to play an important role in outcomes across the life course. The US Department of Housing and Urban Development (HUD) provides housing assistance to 5 million families including 3 million children, yet housing assistance is an understudied social determinant of child health and wellbeing. The benefits of housing assistance may be particularly important for children. Improved conditions during critical periods in childhood may lead to better outcomes throughout the life course. Furthermore, most existing research has used small and geographically-limited samples, relied on self-reported housing status, and failed to identify suitable comparison populations, rendering results potentially biased by unobserved confounders. The objective of this project is to overcome these previous limitations and advance understanding of the relationship between housing assistance and child health, focusing on physical health status, wellbeing, and cardiometabolic risk. The project uses a novel data linkage between the National Health and Nutrition Examination Survey (NHANES), the National Health Interview Survey (NHIS) (expected n's: 2,200 and 3,047, respectively) and HUD longitudinal administrative records. The central hypothesis is that housing assistance leads to improved health and wellbeing for disadvantaged children, although the pattern of this effect may depend on the specific housing program (public housing, housing choice vouchers, multifamily housing). The analysis uses an innovative study design to isolate the causal impact of housing assistance on child health using a pseudo waitlist design. The project examines whether children receiving housing assistance at the time of interview experience better health and wellbeing outcomes than their counterparts who enter housing assistance within 2 years of their interview, the mean length of HUD waitlists (Aim 1). The project also considers whether these effects differ by specific housing program, comparing public housing, housing choice vouchers, and multifamily housing programs (Aim 2). These programs have shown disparate effects in previous research on adults. Finally, the project examines the effects of housing assistance on key intermediate outcomes associated with child health, including: a) parent mental health, b) food insecurity, c) access to medical care, and d) neighborhood context (Aim 3). The results will provide the most comprehensive picture of the potential health impacts of improved housing for a national sample of children, and can inform future public health research, practice, and policies that affect children. This exploratory study will provide preliminary data needed to build a more comprehensive and robust investigation of housing assistance and health, laying the groundwork for our larger research agenda on the impact of housing and neighborhoods on health and wellbeing throughout the life course.